Universal tool for uniformly applying a force to a plurality of components on a circuit board

ABSTRACT

A multiple force tool for applying pressure to circuit components during a manufacturing operation. A plurality of compressed air pressure cylinders are supported on a plurality of horizontal arms over a circuit board. A pressure foot of each compressed air pressure cylinder is extendable when an air controller foot switch is depressed. Positioning of each of the cylinders is afforded along two axes, so that the cylinders may be positioned over components which are to be pressed against the circuit board. Heat sinks may be pressed against components located on the circuit board to bond the heat sinks to the components.

FIELD OF THE INVENTION

The present invention relates to an apparatus and process formanufacturing electronic circuit boards. Specifically, a tool forapplying a force to a component being bonded to a circuit board isdescribed.

BACKGROUND OF THE INVENTION

Electronic circuit boards are manufactured by mounting components on aprinted circuit board. The printed circuit board includes printedcircuit wiring which connects terminals of the components in anelectrical circuit. The electrical components on the board often includea heat sink to maintain the electrical component temperature at a safelevel. The heat sinks are typically applied to circuit board componentswith an adhesive which has good heat transfer characteristics. Duringthe process of bonding the heat sink to a component, the adhesivematerial is applied to the component or heat sink, and a uniform amountof pressure is applied to the heat sink to establish a high strengthbond with the component. The integrity of the bond is maintained byutilizing a uniform amount of pressure on each heat sink being adheredto the components.

As more than one component might require a heat sink, the heat sinks areindividually applied to each component. A fixture holds the componentwithin a press which applies a force to the heat sink, and mustnecessarily be configured for each individual component as they occupydifferent positions on the circuit board. To apply heat sinks todifferent components therefore requires reestablishment of the pressposition versus the component/heat sink position. Additionally, the heatsink sizes change from component to component, and the amount ofpressure applied to different heat sinks, which may be bonded withdifferent adhesives, changes from component to component. These problemshave been addressed in the past by employing custom or unique toolingdevices to accommodate each heat sink size, as well as circuit boardcomponent location on a circuit board, creating inefficiencies in themanufacture of electronic circuit boards.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a press for simultaneouslyapplying a force to multiple components and heat sinks on a circuitboard.

This and other objects of the invention are provided for by a presswhich is capable of simultaneously applying force to multiple componentsof a circuit board assembly. Multiple support channels are providedalong a surface of a pressing tool, which support a number of arms whichextend over a circuit board. A pressure cylinder is supported on each ofthe horizontally extending arms and positioned over a respectivecomponent which is to receive an applied force. The horizontallyextended arms may be positioned along one axis within a respectivesupport channel, while the plurality of pressure cylinders may bepositioned along a second axis coincident with the horizontallyextending arm supporting the cylinder. Thus, the cylinders may bepositioned into alignment with a single component on a circuit board,and, when activated, simultaneously apply the required force to acomponent on the circuit board.

In a preferred embodiment of the invention, the pressure cylinders areoperated by compressed air supplied by a regulated source of compressedair. A foot valve is connected to the source of compressed air whichwhen operated simultaneously applies an actuating pressure to each ofthe compressed air cylinders, which results in an extension of thepiston within the cylinders to apply a force to each component locatedunder the cylinders. The amount of pressure as well as the duration ofthe pressure applied to a component may be accurately controlledensuring uniformity from circuit board to circuit board.

DESCRIPTION OF THE FIGURES

FIG. 1 is an overall isometric view of the multiple force tool inaccordance with a preferred embodiment.

FIG. 2 illustrates a side view of one of the force-applying air pressurecylinders of the device of FIG. 1.

FIG. 3 illustrates a second view of the device of FIG. 1 whichillustrates the positioning of a plurality of pressure cylinders withrespect to a circuit board.

FIG. 4 is another side view of the device of FIG. 1.

FIG. 5 illustrates the structure for supporting each horizontal arm in achannel of the tool.

FIG. 6 is a side section view of FIG. 5.

FIG. 7 is a pneumatic diagram of a pneumatic air controller foroperating each of the air cylinders.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown an isometric view of a multipleforce tool for applying a bonding force to multiple components (three ofwhich are shown) on a circuit board 5 supported on a positioning slide10. When slide 10 is guided into place against the rails of channels 19,20 and 21, each of the three components shown on circuit board 5 may beappropriately aligned with the ends of a plurality of air cylinders 11,12, 13 and 14. Cylinders 11 through 14 may be positioned along two axes.The first axis is coincident with the major axes of support arms 6through 8, and a series of holes 6A, 7A, and 8A along the surface ofeach of arms 6 through 8 provide various locations in which to mount therespective air cylinder 11-14.

Each of the arms, 6, 7 and 8 is supported within a channel 19 through21. The horizontally extending arms 6 through 8 are connected to thechannel by supports 6B, 7B and 8B. The supports are positionable withinthe channel to position a respectively supported air cylinder 11-14along a second axis.

Each of the arms 6 through 8 may have different lengths. The holes 6A,7A and 8A may also be made of one or more slots, to permit positioning arespective air cylinder along the length of an arm 6, 7 and 8.

The air cylinders 11-14 are operated from a air controller 25 which isconnected to a source of compressed air. Compressed air is provided tomanifolds 32, 33 provided by hoses 28, 29, which in turn supplycompressed air to hoses 35-38 for operating each of the air cylinders11-14. The manifolds 32, 33 receive air pressure from the air controller25 and distribute the pressure to each individual air cylinder via hoses35-38.

In this example, two manifolds are provided to accommodate a largernumber of air cylinders.

Each of the air cylinders 11-14 includes a flow control valve 41 through44. In operation, the flow of compressed air is controlled by a footswitch 55 connected by hoses 30, 31 to the air controller 25 to generatea timed pulse of air for operating each of the air cylinders 11-14. Atimer 53 of the air controller 25 establishes the length of an air pulseto be applied to each of the air cylinders 11-14 which in turnestablishes the length of time the piston of each air cylinder isextended against a component on circuit board 5 during a pressingoperation.

The pressure level of the air pulse is established by a control 52 of aregulator. An emergency shut off 50, shuts down the air supply to allthe cylinders when operated. The regulator control 51 regulates the airpressure applied to the air controller 25.

FIG. 2 illustrates the operation of the device with respect to one ofthe air cylinders 13. The air cylinder 13 in FIG. 2 has a piston with apressure foot 13A which is extended as a result of air pressure suppliedthrough the flow control valve 43. The pressure foot 13A forces a heatsink into pressure contact with a circuit board component mounted oncircuit board 5. An adhesive 2 is shown which will bond the heat sink 4to the circuit board component once the heat sink 4 is forced intocontact with the circuit board component 1.

The quality of the resulting bond is controlled in part by the magnitudeof the force applied by pressure foot 13A, as well as the duration ofthe force. As was noted with respect to FIG. 1, the value of the appliedpressure is controlled by the air controller 25, along with the durationof the applied force. The position of the air cylinder 13 along one axisis established by mounting holes 7A of the horizontally extending arm 7.A pair of screws 45 and 46 hold the air cylinder 13 to the arm 7 so thatthe pressure foot 13A is positioned along the axis defined by arm 7aligned with the appropriate component 1.

FIGS. 3 and 4 illustrate two views of the multiforce device whichdemonstrate the versatility of the device for circuit boards havingdifferent component layouts. As shown in FIG. 3, a pair of air cylinders11 and 12 may be included on the same horizontal arm 6. Horizontal arm 6and horizontal arm 7 may be positioned along an axis perpendicular tothe direction of movement of horizontal arm 8 to align the air cylinders41-43 with respect to components on circuit board 5. The positioning ofarms 6 and 7 is provided for by the channel structure illustrated inFIGS. 5 and 6. The channel 19 is bounded by two rails 48 and 49. Rails48 and 49 captivate a lower portion 7C of vertical support 7B. Lowerportion 7C includes a slot 60 which maintains the vertical support 7Bwithin the channel 19. A pair of set screws 61 and 62 provide for fixingthe vertical support 7B to the rails 48 and 49 when the position of thearm 7 has been established.

The air controller 25 is connected to a compressor (not shown) andderives from the compressor air flow for the required air pulse foroperating each of the air cylinders 11-14. A detailed schematic of theair controller 25 is illustrated in FIG. 7. Referring to FIG. 7, airfrom the compressor is supplied to a filter/regulator 70 within the aircontroller 25 which filters and regulates the air pressure from thecompressor. An emergency power-off valve 71 is actuated by an actuator50 to turn off the air supply in an emergency. This would result in eachpressure foot of each air cylinder 11-14 being retracted by a springinternal to each air cylinder. A single pilot valve 72 supplies the airpressure in the absence of the operation of the emergency valve to theremaining components of the air controller.

The operation of the air controller for pressurizing each of the aircylinders 11-14 begins when the foot valve 55 is operated. The airpressure produced from operation of the foot valve 55, is converted intoa short pulse of air by a one shot valve 74. A double pilot valve 75operated from the pulse of air produced by one shot valve 74, to supplyair to regulator 81. The cylinders 11-14 are retracted, when a pulse ofair is sent from OR gate 79 to the double pilot valve. The cycle ofoperating the air cylinders to extend and retract the pressure feet iscontrolled by a pneumatic timer 77. The pneumatic timer 77 is preset togenerate a time interval following activation of the double pilot valve75.

The air pulse supplied to regulator 81 is also applied to the input of atimer 77 to begin timing. Once the set time established by control 55 ofthe timer 77 has elapsed, a reset signal is sent from the timer to ORgate 79, which, as noted above, resets the double pilot valve 75. Thesingle shot valve 78, in an emergency condition also provides a resetair pulse via OR gate 79 to the double pilot valve 75 for resetting thevalve 75. The timer 77 is reset by one shot valve 80, following thereset of the double pilot valve 75.

The air controller 25 provides the pulsed air via regulator 81 to eachof two manifolds 32 and 33. The outputs from the manifolds 32 and 33supply air pressure to the flow control valves 41-44 and air cylinders11-14. A second air regulator 82 may be provided for operating other aircylinders where different air pressures are required.

The flow control valves 41-44 regulate the speed of the air cylinderduring extension of the pressure feet of the air cylinders. As such, itavoids any excessive dynamic forces on the component being pressed.

The air controller 25 provides a uniform application of pressure amongeach of the air cylinders, so that heat sinks, or other components couldbe bonded to the circuit board in one single operation. Multiple aircylinders avoid having to realign the circuit board in order to applyforce to multiple locations on the circuit board, thus savingmanufacturing time and assuring a uniform force application.

Positioning of the arms 6, 7 and 8 along each of the channels 19, 20 and21 may be facilitated by affixing a ruler 88 having position indicia tothe sides of the rails of each of the channels. Thus, the verticalsupports 6B, 7B and 8B may be accurately positioned for a givencomponent layout on each circuit board 5.

The foregoing description of the invention illustrates and describes oneembodiment of the present invention. Additionally, the disclosure showsand describes only the preferred embodiment of the invention, but asaforementioned, it is to be understood that the invention is capable ofuse in various other combinations, modifications, and environments andis capable of changes or modifications within the scope of the inventiveconcept as expressed herein, commensurate with the above teachings,and/or the skill or knowledge of the relevant art. The embodimentdescribed hereinabove is further intended to explain best mode known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other, embodiments and with thevarious modifications required by the particular applications or uses ofthe invention. Accordingly, the description is not intended to limit theinvention to the form disclosed herein. Also, it is intended that theappended claims be construed to include alternative embodiments.

What is claimed is:
 1. A multiple force tool for establishing a pressureon circuit board components during manufacture of a circuit boardbearing said components comprising:first, second, and third channelssupporting a plurality of horizontal arms, said channels being locatedabout the periphery of a surface which is adapted to support saidcircuit board so that said horizontal arms extend over said circuitboard; a plurality of compressed air pressure cylinders supported onsaid horizontal arms, having a pressure foot which is extendable inresponse to compressed air and is adapted to apply a force on acomponent of said circuit board located beneath said pressure foot; anda source of compressed air connected to said compressed air pressurecylinders, operable in response to a foot valve for extending saidpressure feet against said circuit components including a timer meanswhich operates in response to a closure of said foot valve to produce atimed pulse of compressed air to said compressed air cylinders wherebysaid pressure feet are extended for a period of time controlled by saidtimer.
 2. The multiple force tool according to claim 1 wherein saidsource of compressed air supplies said timed pulse of compressed airhaving a preset duration and magnitude.
 3. The multiple force toolaccording to claim 1 wherein said compressed air is supplied through aflow control valve to said compressed air pressure cylinders forregulating the speed of extension of said pressure foot.
 4. The multipleforce tool according to claim 2 further comprising a pressure regulatorconnected to said timer means for receiving said pulse of compressed airand connected to a manifold which supplies said pulse of compressed airto said compressed air cylinders.
 5. The multiple force tool accordingto claim 4 further comprising a flow control valve connected betweeneach of said compressed air cylinders and said manifold.
 6. The multipleforce tool according to claim 5 wherein said horizontally extending armsare positionable along said channels to vary the location of saidpressure cylinders along a first axis.
 7. The multiple force toolaccording to claim 5 wherein said horizontally extending arms includemeans for positioning said pressure transducers along a second axis. 8.The multiple force tool according to claim 7 wherein said channelsinclude position indicia for establishing a position coordinate for saidpressure cylinders along said first axis.